This invention relates to valve shutoff mechanisms for automatically operating a gas valve or the like to shut off the flow of fluid in a pipeline in response to an earthquake, temperature changes and/or an electrical or mechanical signal generated external to such mechanisms.
Vibration sensitive devices are known which are designed to respond to earthquake vibrations of a predetermined magnitude in order to shut off a valve in a gas conduit or the like. Such devices function as a safety mechanism for reducing the possibility of explosion due to ruptured gas connections downstream of the valve and within a building structure, such as a private dwelling, an apartment building, an office building or the like. In my previously filed and issued U.S. Pat. No. 4,161,183, issued July 17, 1979, the disclosure of which is hereby incorporated by reference, a vibration sensitive valve operating apparatus is disclosed and claimed which avoids disadvantages inherent in known earlier devices, and which can be tuned to vibrations of a predetermined magnitude so as to avoid false triggering of the device in response to seismic vibrations unrelated to earthquakes, such as vibrations caused by passing trucks or frictional forces resulting from mechanical loading. In addition my earlier invention is designed with a protective enclosure for the latch and trigger mechanisms to avoid accidental triggering by a prowling animal or small child. Further, my earlier invention is compatible with a wide variety of valve mechanisms, is capable of being installed without the requirement of special technical skills, and can be left in situ for long periods of time without suffering functional impairment due to exposure to the elements.